chromosome condensation in porcine oocytes. However, chromosome alignment could not be assessed due to what appears to be a species specific arrest at the GV stage. If chromosome condensation in mouse oocytes is not affected by ZM447439, the chromosome alignment defect must be due to an AURKB function other Danoprevir Proteasome inhibitor than phosphorylation of histone H3. In mitosis, AURKB is a chromosomal passenger protein that, along with INCENP, survivin and borealin regulates kinetochore microtubule attachment to chromosomes and is essential for proper chromosome tension, and thus, chromosome segregation . Disruption of AURKB,s function causes chromosome alignment defects that are an early sign of aneuploidy because cells are unable to correct improper microtubule kinetochore attachments .
The enrichment of AURKB at kinetochores at Met I and its partial rescue of the chromosome misalignment phenotype caused by ZM447439 suggests that MDV3100 915087-33-1 AURKB is responsible for regulating chromosome alignment at Met I. Future studies on the role of AURKB at Met I kinetochores will be important for elucidating the molecular mechanisms that contribute to the high degree of aneuploidy due to nondisjunction during the first meiotic division in oocytes. MATERIALS AND METHODS Oocyte Collection and Culture Six week old female CF 1 mice were injected intraperitoneally with 5 IU of eCG . Meiotically competent, germinal vesicleintact oocytes were collected as previously described into MEM/PVP , and 25 mM HEPES at pH 7.3 containing 2.5 μM milrinone to inhibit meiotic resumption .
Cumulus cells were removed by pipetting and oocytes were transferred into milrinone free CZB for meiotic maturation at 37C and 5% CO2. All animal experiments were approved by the Institutional Animal Use and Care Committee and were consistent with NIH guidelines. SHUDA et al. Page 7 Mol Reprod Dev. Author manuscript, available in PMC 2011 October 5. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript Quantitative RT PCR Total RNA was extracted from GV intact oocytes and MII eggs using the Absolutely RNA Microprep Kit with the addition of 2 ng of Egfp RNA to the lysis buffer . Reverse transcription was performed using random hexamers and Superscript II reverse transcriptase as previously described .
The Ct values were determined by real time PCR using an ABI Prism 7000 and the following custom Taqman assays : AurkA F 5′GTCTCACTGTGGGAAACTTACCA 3�? R 5′GCCTGGTGACCCAATAAGTTATACA 3�? probe FAM CTG TGTCGTAGCCT, TCA, AurkB F 5′GGTGCTCACGACCACTGT 3�? R 5′CTCGAAGGCCCCAGATTCC, 3�? probe FAM CCAGGACTGGGTGTTACA, AurkC F 5�?AAGCGCGATCTGGAAAC, CT 3�? R 5′GACACACACACTGGTAATCCACTAG 3�? probe FAM ACAGCGGCACT, CAAG. Assay on demand, Mm00660092 m1, was used to detect Prkaca. Relative expression was calculated using the comparative Ct method where the samples were normalized to Egfp levels and the Prkaca level in a GV intact oocyte was set to 1. Three independent samples were collected and Ct values were determined in duplicate from 4 oocyte equivalents. Immunocytochemistry Following meiotic maturation to the indicated stage, oocytes and eggs shown in Figures 2, 4, and 5 were washed in phosphate buffered solution and fixed for 10 min in cold methanol .
The oocytes and eggs were incubated in blocking buffer consisting of 10% normal goat serum , 4% BSA, and 0.1% Triton X 100 either overnight at 4C or for 1 hr at room temperature , respectively. The cells were then incubated with a 1:500 dilution of rabbit anti AURKA antibody or a 1:200 dilution of rabbit anti AURKC antibody in blocking buffer for 1 hr at RT followed by a 1:200 dilution of monoclonal anti β tubulin clone TUB2.1 antibody , 1:100 dilution of monoclonal anti γ tubulin , or a 1:30 dilution of CREST anti serum in blocking buffer for 1 hr at RT. These incubations were followed by a 1:250 dilution of goat anti rabbit antibody conjugated to AlexaFluor568 and a 1:200 dilution of goat anti mouse antibody conjugated to FITC or a 1:100 d

TPase. Typical results are shown one of five experiments. doi: 10.1371/journal.pone.0029269.g003 interaction between PP2A and the Na, K-ATPase PLoS ONE | Published in PloSOne fourth December 2011 | Volume 6 | Issue 12 | e29269 because of steric competition between these two polypeptides for the same or overlapping binding sites of the subunit. To this M Opportunity to test, we Vismodegib Hedgehog inhibitor performed a competitive binding experiment. The competition between arrestin binding and PP2A C subunit as shown in Figure 6, which destroyed PP2A C-subunit partially Rt the relationship between the ATPase Na, K, and arrestin second For two arrestin 2, and PP2A C-subunit of Na, K-ATPase big interact en cytoplasmic loop, the PP2A block C subunit directly arrestin binding to the big s cytoplasmic loop of the ATPase Na, K 7B shows pull-down experiments to assess the binding between a GST-protein with the big s cytoplasmic loop of the ATPase Na, K and arrestin 2 in the presence of PP2A to test C-subunit.
PP2A C subunit strongly inhibited in 4 In vitro translation of PP2A and GST pull-down building with the big s cytoplasmic loop of GSK1904529A IGF-1R inhibitor the Na, K-ATPase subunit. PP2A A and C subunit proteins Were prepared by in vitro translation and GST pull-down was performed using GST alone or GST Na, K-ATPase big manufactured en cytoplasmic loop performed. A. proteins Used for GST pull down were F Detected staining with Coomassie Brilliant Blue. PP2A C subunit and A subunit were detected by Western blotting with anti-HA antibody Body and anti-Flag or. The PP2A C subunit, but not the A subunit, with GST Co Na, K-ATPase.
Typical results showed one of three experiments. doi: 10.1371/journal.pone.0029269.g004 Figure 5 Deletion of the big s cytoplasmic loop of Na, K-ATPase subunit and GST-pull down of PP2A with constructs of GST. A. HA labeled PP2A C-subunit in COS cells and cell lysates was expressed were incubated with GST-fusion proteins. Csubunit PP2A was determined by Western blotting with anti-HA antibody Body and GST-fusion proteins Were CBB-R Staining is detected. Not only N-terminal segments, but also the C-terminal, half of the big s cytoplasmic loop binds to the C subunit PP2A. Typical results are shown one of four experiments. B. flag tagged PP2A A subunit was expressed in COS cells and cell lysates were incubated with GST-fusion proteins.
PP2A A subunit was determined by Western blotting with an antibody Body Anti-Flag and GST-fusion proteins Were CBB-F Staining is detected. The A subunit of PP2A, together with executed Filled cathedral Ne A of the Na, K-ATPase subunit. Typical results showed one of three experiments. doi: 10.1371/journal.pone.0029269.g005 interaction between PP2A and the Na, K-ATPase PLoS ONE | Published in PloSOne fifth December 2011 | Volume 6 | Issue 12 | E29269 arrestin binding to the large cytoplasmic loop of the ATPase en Na, K. 7C shows the reverse experiment, in which the interaction between the protein GST by the big s cytoplasmic loop of Na, K-ATPase and PP2A C subunit was tested in the presence of 2 arrestin. Shown in contrast to the results in Figure 7B, PP2A C bond to Na-K-ATPase subunit was little inhibited in the presence of arrestin second Coomassie Brilliant Blue R Best coloring Firmed that equal amounts of GST protein in all the canals used len.
These data suggest the interesting M Possibility that the affinity t of PP2A C-subunit for binding to the sodium pump big cytoplasmic loop fusion protein significantly, he h Ago than that of arrestin. The localization of Na, K-ATPase in COS cells expressing arrestin and PP2A, we have shown that the induced overexpression of arrestin redistribution of ATPase Na, K to intracellular Ren compartments. Since the C-subunit PP2A inhibits arrestin binding, we studied the effect of C-subunit of the PP2A localization of Na, K-ATPase expressed cooperation with arrestin. COS cells were transfected with H85N and Na, K-ATPase subunit transfected B of the presence or absence of arrestin 2 and / or PP2A C subunit and the cells were found Rbt

Blot analysis of ATM expression ARQ 197 c-Met Inhibitors in cells with miR-18a mimic implied or miR-18a-transfected inhibitory oligonucleotides. C, Western blot analysis showed that the GFP expression indicated in the cells. -Tubulin was used as a loading control. D, luciferase assay on cells that mimic the specified reporter pGL3-ATM 39UTR with increasing amounts of miR-18a or miR-18a inhibitor oligonucleotides were transduced. E, luciferase assay of transduced cells with the indicated pGL3-ATM 39UTR or pGL3-ATM 39UTR-MUT reporter with increasing amounts of miR-18a mimic oligonucleotides. F, expression of miR-18a and correlation, and ATM in nine fra YEARS Riger pr Parried human tissue for breast cancer. The error bars represent the mean 6 SD of three independent Ngigen experiments. * P, 0.05. doi: 10.1371/journal.
pone.0025454.g002 miR-18a is in the DNA involved in the response Sch PLoS ONE | Published in PloSOne 4 September 2011 | Volume 6 | Issue 9 | e25454 NBECs in drastically reduced expression of ATM. Moreover, it was Western blot analysis, that controlled in response to IR treatment, the expression of p-CHK2 H2AX and 53BP1 were in the p-miR-18a NVP-BVU972 c-Met Inhibitors transfected NBECs much lower than that in transfected cells the vectors. In addition, clonogenic assay showed that overexpression of miR-18a makes NBECs hypersensitive to IR. Taken together, our results indicate that the upregulation of sufficient miR18a in NBECs to the activation of ATM and HRR events w Influence during IR treatment. The inhibition of miR-18a increased Ht ATM expression and cell sensitivity to radiation is reduced, we then examined the effect of inhibition of miR-18a expression of ATM and HRR.
As in Figure 5A, L Between miR-18a after transfection of miR-18a inhibitor not only the expression of ATM in cell lines of breast cancer both increased Hte show, but clearly the level of prices increased Ht phosphorylation of H2AX and 53BP1 . Zus Tzlich we found that inhibition of miR-18a significantly the H FREQUENCY FCR and reduced the proportion of cells that were in Figure 3. miR-18a affects the ATM-signaling pathway. A Western blot analysis of ATM expression, total and phosphorylated CHK2 CHK2 protein in cells with or without IR were treated. -Tubulin was used as a loading control. B, the corresponding Western blot analysis of expression of c-H2AX, 53BP1 phosphorylated and total protein in cells treated with 53BP1 IR.
-Tubulin was used as a loading control. C and D, pl Sentative photos and quantification of IR-induced c-H2AX and 53BP1 foci were in breast cancer cells with NC, miR-18a or scramble siRNA transfected analyzed ATM specified. The number of households with at least 300 cells were hlt gez. The error bars represent the mean 6 SD of three independent Ngigen experiments. * P, 0.05. doi: 10.1371/journal.pone.0025454.g003 miR-18a is in the DNA involved in the response Sch PLoS ONE | 4 Figure e25454 | Published in PloSOne 5 September 2011 | Volume 6 | Issue 9 miR-18a reduces the H FREQUENCY of HRR cells and enhances cell sensitivity to radiation. At the DSB-induced HRR test showed that the overexpression of miR-18a, H FREQUENCY decreased the spontaneous HR in HT1080-1885 cells.
Western blot analysis of expression of ATM and HA-tagged I-SceI endonuclease. -Tubulin was used as a loading control. B, miR-18a overexpression or silencer Fighters increased ATM expression Ht the sensitivity of breast cancer cells to IR treatment. However, overexpression of miR-18a mimic any additionally USEFUL sensitivity to IR in ATM cells had been silenced. The ability Lebensf Showed the cells were, after the indicated doses of c-radiation by the clonogenic assay for cell survival analyzed. The error bars represent the mean 6 SD of three independent Ngigen experiments. * P, 0.05. doi: 10.1371/journal.pone.0025454.g004 Figure 5 The inhibition of miR-18a, Inc.

cancer cell lines. Importantly, the breast adenocarcinoma-like cell line MCF7 and the ductal carcinoma-like cell Flt Signaling lines BT474, HCC70 and BT549 all showed resistance to BEZ-235 treatment upon expression of ICN1 24. To ask if NOTCH activation may also confer PI3K/mTOR inhibitor resistance in other tumor types we analyzed a publicly available dataset created by GlaxoSmithKline, comprising over 300 molecularly characterized and drug treated cell lines. This revealed a significant correlation between low expression of NUMB, a negative regulator of NOTCH, and resistance to PI3K/mTOR inhibition in cell lines derived from various tumor types, including melanoma and hepatocellular carcinoma 32. These results suggest that uncoupling proliferation from the PI3K/mTOR pathway via NOTCH1 activation may be a more general phenomenon across cancer cell lines. ICN1 overrides mTORC1 signaling via c-MYC transcription Ribosomal S6 Kinase GDC-0980 1032754-93-0 and the eukaryotic translation initiation factor 4E-binding protein 1 are main effector molecules of mTORC1 and their phosphorylation stimulates protein translation 29. Interestingly, S6K and 4EBP1 phosphorylation was equally inhibited in ICN1 expressing cells as in control cells. This suggests that ICN1 uncouples mTORC1 signaling from proliferation by a downstream mechanism. Upon closer inspection of the screening data we found that cells transduced with c-MYC also displayed remarkable resistance to BEZ-235 and other PI3K inhibitors. Notably, the c-MYC expression level and shift in the BEZ-235 dose-response curve was comparable to ICN1 expressing cells, indicating that c-MYC may be the main transcriptional target conferring the resistance 33-35. In agreement with this, overexpression of the NOTCH canonical target genes HES1, HEY1 or HEY2 did not confer BEZ-235 resistance to MCF10A cells. Furthermore, c-MYC induction in NOTCH-deltaE expressing cells was γ-secretase sensitive and the Muellner et al. Page 5 Nat Chem Biol. Author manuscript, available in PMC 2012 May 1. UKPMC Funders Group Author Manuscript UKPMC Funders Group Author Manuscript NOTCH3 intracellular domain that in these cells did not induce c-MYC expression also did not confer resistance. To investigate directly if c-MYC induction was required for resistance to BEZ-235 inhibition, we inhibited c-MYC expression by RNAi in ICN1 cells. As predicted, knockdown of c-MYC to levels comparable to control MCF10A cells completely reversed the resistance to BEZ-235. This was not due to a general cytotoxic effect of c-MYC knockdown as the increased sensitivity to Aurora kinase inhibitors was also reverted. These experiments show that c-MYC induction by ICN1 is necessary and sufficient for the PI3K/mTOR resistance. Finally, the notion that c-MYC upregulation confers resistance to PI3K/mTOR inhibition prompted us to investigate if cell lines with c-MYC gene amplification also displayed this characteristic. Indeed, c-MYC amplification was observed significantly more often among PI3K/mTOR inhibitor resistant cell lines. This effect was specific as c-MYC amplified cells lines were not resistant for Aurora kinase inhibition but rather showed a trend towards synthetic lethality, which is in agreement with our previous findings. Thus, we conclude that NOTCH pathway activation uncouples PI3K-mTOR signaling from proliferation by induction of c-MYC and this may have direct implications for patients treated with drugs targeting this pathway. DISCUSSION We identified a novel mechanism of resistance to PI3K inhibitors in breast cancer cell lines by activating NOTCH signaling and induction of c-MYC. NOTCH activation occurs in a subset of breast cancers and is associated with tumor progression and poor prognosis and MYC amplification is a relative frequent event 10, 3

ponse, with 2 CR, 3 CRi, and 3 PR. Neither of the studies evaluated AML cells after exposure to AZD1152 HQPA to correlate polyploidy with cell viability and should be the focus of future research. There are currently multiple phase I and II clinical trials ongoing evaluating AZD1152 in multiple solid and hematologic malignacies.28 Although the clinical relevance of Alvocidib CDK inhibitor this is unknown, resistance to AZD1152 has been induced in cell cultures of colorectal and pancreatic cancers.80 These cell cultures were purposefully incubated with sublethal doses of AZD1152 with the intent of causing resistance and elucidating the cause. This study determined that both cell lines upregulated the ABC transporter, MDR1, and BCRP, both of which are cellular efflux pumps for numerous pharmaceutical agents, leading to a 100 fold higher resistance to AZD1152 than wild type cells.
Furthermore, upregulation of MDR1 and BCRP by AZD1152 produced crossresistance to the pan aurora kinase inhibitor VX 680/MK 0457.80 3.1.3 GSK1070916 GSK1070916, discovered through cross screening and structureactivity relationship refinement, competitively binds to aurora B and C kinases with far greater selectivity than aurora A.81 Of note is the extremely MK-2206 slow rate of dissociation, with dissociation half life of 480 minutes for aurora B kinase, compared to dissociation half life of AZD1152 of 30 minutes. Due to slow offset of activity, this compound may confer advantages in slower growing tumors and/or less frequent dosing. Preclinical studies in cell tissue cultures and murine models show efficacy in tumors of breast, colon, non small cell lung, CML, and AML.
82 No human data are currently available, but a phase I trial in advanced solid tumors in underway in the United Kingdom administering GSK1070916 intravenously over 1 hour once daily on days 1�? every 21 days.28 Green et al. Page 7 Recent Pat Anticancer Drug Discov. Author manuscript, available in PMC 2011 February 15. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript 4.0 Dual Aurora A and Aurora B Kinase Inhibitors 4.1 ZM447439 ZM447439 is one of the first AKIs to be developed and served as a template for AZD1152.83 Despite inhibiting aurora A and B equipotently, the phenotype induced in tumor cells following exposure to ZM447439 is more consistent with aurora B kinase inhibition.
84 This incongruency may be due more selective in vivo aurora B kinase inhibition, though data are lacking. Early work with ZM447439 focused on elucidation of aurora kinase activity, rather than drug development. Preclinical studies with ZM447439 in cell lines of AML85, neuroendocrine tumor86, breast cancer87, and mesothelioma88 have led to understanding of importance of aurora kinase inhibition. ZM447439 is included in this review for historical context as the current use is restricted to exploratory laboratory studies. 4.2 JNJ 7706621 Also a potent inhibitor of the family of cyclin dependent kinases CDK1, CDK2, and CDK3 , JNJ 7706621 displays high affinity for both aurora A and B kinases , making it active from S through G2 phase of cell cycle.89 As seen with other members of the dual inhibitor class, exposure to JNJ 7706621 creates a phenotype more similar to aurora B kinase inhibition.
Little is published in manuscript or abstract form about JNJ 7706621 and no clinical trials are currently open.28 4.3 AT9283 Discovered through fragment based high throughput X ray crystallography techniques, AT9283 is equally potent at inhibiting aurora A and B kinases, in addition to inhibiting JAK2, JAK3, STAT3, BCR Abl , Tyk2 and VEGF, with IC50 values ranging from 1�?30nM.90 Preclinical studies in human tumor cell lines and murine xenograft models of colorectal, ovarian, non small cell lung, breast and pancreatic carcinom

at pH 7.4, 3 mM ATP, 0.8 mM ADP, 5 mM succinate, and 2 M rotenone for respiration. Mitochondrial suspensions diluted in assay buffer were exposed to Ca2, GS NO, or H2O2 for 10 min and centrifuged at 12,000g for 5 min. The supernatant was Cuscutin Bergenin collected, and 15 l aliquots were run on a SDS PAGE gel to detect the release of cytochrome c by immunoblotting. To examine the effect of AA on cytochrome c release, AA or buffer only was added to mitochondria 5 min before the start of the assay and kept in the reaction mixture during the assay. Oxygen Glucose Deprivation HT 22 hippocampal neuronal cell line was maintained in a vented filter capped T75 culture flasks containing Dulbecco,s modified Eagle,s medium supplemented with 10% fetal bovine serum at 37 in an atmosphere containing 5% CO2 and 95% air.
When the cells were 75% confluent, they NVP-BKM120 1202777-78-3 were detached from the flasks with 0.05% trypsin EDTA. After the addition of media containing 10% FBS, cells were harvested and centrifuged at 1,500 rpm for 2 min. Cells were then seeded at a density of 0.8 × 106 in 35 mm individual culture dishes or 96 well culture plates. Experiments were initiated 24 hr later. In all experiments, cells were used from passages 5 10. OGD was induced in cultures as described by Panickar et al., with minor modifications. Briefly, cultures were washed twice with a balanced salt solution of the following composition : NaCl 116, KCl 5.4, CaCl2 1.8, MgSO4 0.8, NaH2PO4 0.83, NaHCO3 24, and phenol red 0.001 w/v, pH 7.4. After washes, BSS was added to the cultures and they were placed in an airtight container and continuously flushed with 95%N2/5%CO2 for 5 hr.
After the end of OGD, regular medium Krishnamurthy et al. Page 4 J Neurosci Res. Author manuscript, available in PMC 2010 September 19. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript was added to the cultures and returned to normal conditions for later assays on viability or mitochondrial function. Alamar Blue Cell Viability Assay Cell viability was assayed in cultures by measuring Alamar blue reducing activity, an index of mitochondrial function, as described by Nonner et al.. At 24 hr after the end of OGD, Alamar blue was added to cultures in the 96 well plate at a dilution of 1:20. This dye was excited at 535 nm and fluorescence emission monitored at 590 nm with a plate reader.
The difference between a first reading taken immediately after dye addition and a second reading taken after 40 min of incubation at 37 was used as an index of Alamar blue reducing activity. One advantage of using this dye is that brief incubation with this dye does not harm cells, and, after washout, additional assays can be performed on the same cultures if necessary. Measurement of Mitochondrial Membrane Potential Changes in inner mitochondrial membrane potential were measured with the fluorescent dye TMRE, following the protocol described by Panickar et al., with minor modifications. Immediately at the end of OGD, BSS was removed and cells were loaded with TMRE in regular media and returned to the normal culture incubator for 20 min. Cultures were washed with PBS, and fluorescence images were captured with a Nikon TE2000 inverted fluorescent microscope and Roper Fast Monochrome cooled camera.
At least 10 random image fields having a similar degree of cell density were analyzed. Exposure time was kept constant within each experiment. Fluorescent intensities were analyzed by using a combination of the Nikon Elements program and macros written for V. In each image field, the total number of pixels was quantified on a gray scale, and the average intensity was obtained and expressed as mean SEM of average intensity of the total number of cells in each experimental group. Plasma membrane depolarization induced by KCl in sep

nsitive to IC87114. Our findings suggest that PI3K activation downstream of the activated FcεRI in vitro is biphasic, with p110γ being activated before p110δ upon FcεRI engagement. p110γ, but not p110δ, is dispensable for allergic responsiveness ABT-888 PARP inhibitor in vivo Mast cells in vivo are exposed to stimuli from the microenvironment other than Ag which can modulate the FcεRI response, and it is therefore not always possible to extrapolate in vitro observations such as those shown in Fig.4, A and B, to the organismal context. We therefore tested the in vivo allergic response of γKO and δD910A mice, side-by-side in the same experiment and using mice on the same genetic background. Mice were sensitized locally by injection of Ag-specific IgE and challenged systemically 24 h later with DNP-HSA.
Thirty minutes later, the mast cell response was quantified by measuring extravasated Evans blue. In line with our previously published results in δD910A mice on the BALB/c genetic background , inactivation of p110δ on the C57BL/6 background led to a significant reduction in IgE/Ag-dependent vascular permeability in the ears of sensitized mice. Similar results were YN968D1 EGFR inhibitor observed in the back dermis. Surprisingly,γKO mice did not show reduced in vivo allergic responses. To exclude that altered PCA responses in gene-targeted mice are related to developmental defects, we next pharmacologically intervened with PI3K function using isoform-selective PI3K inhibitors. Treatment of WT mice with the p110δ-selective inhibitor IC87114 at doses which do not affect p110γ consistently diminished the allergic immune response by �?0%.
This milder reduction upon pharmacological, compared with genetic, inactivation of p110δ most likely relates to the reduced number of mast cells in the ears of δD910A mice , as previously discussed , and the notion that IC87114, in contrast to genetic inactivation, is not expected to provide full inhibition of p110δ as is the case in homozygous δD910A mice. In contrast to IC87114, the p110γ-selective compounds AS-604850 and AS-252424 had no significant impact on the allergic response , in line with our observations in γKO mice. Administration Ali et al. Page 6 J Immunol. Author manuscript; available in PMC 2009 February 16. UKPMC Funders Group Author Manuscript UKPMC Funders Group Author Manuscript of the p110β-selective compound TGX-155 also did not impact on the acute allergic response.
Discussion In this manuscript, we report that we have found no evidence that p110γ, in isolation, plays a significant role in the in vivo allergic cascade. This appears to be in contradiction with previous work, which suggested that p110γ is essential for and is the only PI3K subunit which drives the in vivo IgE/Ag-triggered allergic response. It is possible that the proposed GPCRdriven auto/paracrine signaling amplification mechanism, largely based on in vitro observations on cultured mast cells , may not be operational in vivo. This conclusion is in line with the observation that KO mice for A, the main adenosine receptor, retain normal IgE/Ag-dependent PCA responses, despite a complete abrogation of adenosine responsiveness.
Differences in genetic backgrounds of mice could also contribute to the discrepancies between our studies and earlier work. Indeed, previous studies in which p110γ function was assessed used mice bred onto the 129sv background, in contrast to our studies in which we used C57BL/6 mice and BALB/c. However, why a reduced sensitivity of γKO mice to adenosine would be retained across genetic backgrounds, in contrast to responsiveness to allergic responses, is difficult to explain. For a molecule to have an essential role in a proces